ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 27 



the various types. There is (1) a northern province belonging to the 

 Palaearcric region : (2) an equatorial province showing affinities with the 

 molluscan fauna of tropical America and tlie Indian peninsula ; and (3) 

 an australo-african province, with a very archaic fauna, approaching that 

 of Patagonia, Australia, and New Zealand. Many very interesting con- 

 clusions are drawn as regards geographical distribution. 



Arthropoda. 

 a. Insecta. 



Outlines of Entomology.* — 0. W. CEstlund has published a student's 

 guide to the study of entomology. It is of the nature of a synopsis, 

 giving terse and clear notes on the various systems in their structural 

 and functional aspects, and its particular characteristic is that the 

 entomological facts are used to illustrate biological methods and results. 



Case of Defensive Mimicry.! — J. Bourgeois refers to G. A. K. 

 Marshall's observation of Geria gamblana (one of the Diptera) visiting- 

 flowers in company with Polistes marginalis (one of the Hymen optera). 

 He has observed a similar case. He saw Geria conopsoides visiting the 

 wounds on the trunk of a horse-chestnut along with the Hymenopteron 

 Odynerus crassicornis. Both visited the tree with the same end — to lick 

 the exudation, and the Diptera were doubtless protected by their 

 Batesian mimicry of the formidable Hymenoptera. 



Studies on Hymenopterous Parasites.:}: — F. Silvestri has studied 

 I'rospalta berlesi, a Hymenopterous parasite of Diaspis, and points out 

 among other interesting facts that no adult male was found among 

 many hundreds of specimens. The species may be permanently par- 

 thenogenetic. 



The author also describes the development of Ageniaspis fuscicollis 

 Dalm.,§ giving details regarding the maturation, fertilisation and seg- 

 mentation of the ova. In the case of the parthenogcnetic ova, as in 

 those which are fertilised, there are two polar bodies, which remain 

 distinct and form what Marchal called the paranucleus of the tropham- 

 nion, dividing directly and irregularly. The protoplasm of the egg 

 does not wholly go to form embryonic cells, the peripheral part forms 

 an involucre, which Marchal calls the trophamnion. The polar part of 

 the ooplasm and the polar bodies have a protective and nutritive role in 

 relation to the embryonic part. During the formation of the polar 

 bodies the nucleolus remains unchanged in the posterior part of the 

 ovum ; it passes into one of the first two segmentation cells, and seems, 

 as in Litomastix truncatellus, to have a retardative action on the cell in 

 which it occurs, and to retain a determinant of the genital cells. From 

 one ovum 10-15 embryos develop. There are three generations in a 

 year as in the insect victimised, Prays oUellus Fabr. 



Another form studied by Silvestri is Encyrtus aphidivoras. It is 



* Outlines of Entomology. I. Anatomy and Physiology. Minneapolis, 1909, 

 44 pp. t MT. Schweiz. Entom. Ges., xi. (1909) pp. 395-6. 



% Boll. Lab. Zool. Scuola Agric. Portici, iii. (1909) pp. 22-8 (6 figs.). 

 § Tom. cit., pp. 29-85 (2 pis. and 42 figs.). 



